Conditioning system of the free cooling type for environments and particularly for computing centers, method of operation of such system, and apparatus for carrying out such method

ABSTRACT

A conditioning system of the free cooling type for environments and particularly for computing centers, which comprises:
         a conditioning unit of the free cooling type, which in turn comprises an air/air heat exchanger, inside which two air flows exchange heat, a primary air flow, from and toward an environment to be air-conditioned, and a secondary air flow, or process flow, drawn from outside, and evaporative cooling elements using water,   first fans for moving the primary air flow,   second fans for moving the secondary air flow,   detectors for detecting temperature and humidity for the primary air flow and the secondary air flow at the inlet and at the outlet of the conditioning unit,   detectors for detecting the flow-rate of the primary air flow and of the secondary air flow,   an electronic control and management unit adapted to collect and process the data detected by the detectors and adapted to determine, on the basis of the outside humidity and temperature values and of the demand for cooling, the operating cost without the use of water and with a variable use of water.

The present invention relates to a conditioning system of the freecooling type for environments and particularly for computing centers, toa method of operation of such system, and to an apparatus for carryingout such method.

Conditioning systems of the free cooling type are known today and arewidespread, for environments and particularly for computing centers, ofthe type comprising:

-   -   a conditioning unit of the free cooling type, which in turn        comprises an air/air heat exchanger, inside which two air flows        exchange heat, a primary air flow, from and toward an        environment to be air-conditioned, and a secondary air flow, or        process flow, drawn from outside, and an evaporative cooling        unit using water for the primary air flow,    -   first fans for moving the primary air flow,    -   second fans for moving the secondary air flow.

Usually an evaporative conditioning unit, i.e. with cooling means usingwater, is set up to optimize the overall cost of electricity and water.

On the market, however, such conditioning units are usually set at thefactory to start by default with operation using water once the air hasreached a certain dry-bulb temperature, therefore irrespective of theoutside humidity.

Such setting is performed on the basis of a specific demand for cooling,without taking account of any variations of that demand.

Furthermore, since such default operation setting does not take accountof the actual efficacy of the evaporative system at different relativehumidity levels for the same outside temperature, this means that beforeactuating the external fans at maximum speed in dry mode, i.e. withoutengaging the evaporative means, in order to provide the cooling powerrequired, the unit starts using water anyway in order to obtain anevaporative cooling effect.

The aim of the present invention is to provide a conditioning system ofthe free cooling type for environments and particularly for computingcenters, which is capable of also optimizing consumption based on anyvariations of the demand for cooling.

In particular, an object of the invention is to provide a conditioningsystem that is capable of evaluating the actual efficacy of theevaporative system at different relative humidity levels for the sameoutside temperature.

Within the above aim, an object of the invention is to provide a methodof operation of such system.

Another object of the invention is to provide an apparatus for carryingout such method.

This aim and these and other objects which will become better apparenthereinafter are achieved by a conditioning system of the free coolingtype for environments and particularly for computing centers, of thetype comprising:

-   -   a conditioning unit of the free cooling type, which in turn        comprises an air/air heat exchanger, inside which two air flows        exchange heat, a primary air flow, from and toward an        environment to be air-conditioned, and a secondary air flow, or        process flow, drawn from outside, and evaporative cooling means        using water,    -   first fans for moving said primary air flow,    -   second fans for moving said secondary air flow,

said conditioning system being characterized in that it comprises:

-   -   means for detecting temperature and humidity for the primary air        flow and the secondary air flow at the inlet and at the outlet        of said conditioning unit,    -   means for detecting the flow-rate of the primary air flow and of        the secondary air flow,    -   an electronic control and management unit adapted to collect and        process the data detected by said detection means and, on the        basis of such detected data, adapted to determine, on the basis        of the outside humidity and temperature values and of the demand        for cooling, the operating cost without the use of water and        with a variable use of water, and, on the basis of the operating        cost, to activate a wet operating mode in which the evaporative        cooling means using water are active or a dry operating mode in        which the evaporative cooling means using water are inactive.

Further characteristics and advantages of the invention will becomebetter apparent from the detailed description that follows of apreferred, but not exclusive, embodiment of the conditioning systemaccording to the invention, which is illustrated for the purposes ofnon-limiting example in the accompanying drawings wherein:

FIG. 1 is a schematic view of a conditioning system according to theinvention;

FIG. 2 is a further schematic view of the conditioning system accordingto the invention;

FIG. 3 is a schematic view of a method of operation of the conditioningsystem according to the invention;

FIG. 4 is a schematic view of the flow of execution of a first part ofthe method shown schematically in FIG. 3;

FIG. 5 is a schematic view of the flow of execution of a second part ofthe method shown schematically in FIG. 3;

FIG. 6 is a schematic view of the flow of execution of a third part ofthe method shown schematically in FIG. 3.

With reference to the figures, a conditioning system of the free coolingtype for environments and particularly for computing centers isgenerally designated with the reference numeral 10.

Such conditioning system 10 comprises:

-   -   a conditioning unit of the free cooling type 11, which in turn        comprises an air/air heat exchanger 12, inside which two air        flows 13, 14 exchange heat, a primary air flow 13, from and        toward an environment to be air-conditioned 15, and a secondary        air flow 14, or process flow, drawn from outside, and        evaporative cooling means using water 16, better described        hereinbelow;    -   first fans 17 for moving the primary air flow 13,    -   second fans 18 for moving the secondary air flow 14.

The peculiarity of the conditioning system 10 according to the inventionconsists in that it comprises:

-   -   means 19, 20, 21, 22, described below, for detecting temperature        and humidity for the primary air flow 13 and the secondary air        flow 14 at the inlet and at the outlet of the conditioning unit        11,    -   means 23 and 24, also described below, for detecting the        flow-rate of the primary air flow 13 and of the secondary air        flow 14,    -   an electronic control and management unit 25 adapted to collect        and process the data detected by the detection means 19, 20, 21,        22, 23, 24 and, on the basis of such detected data, adapted to        determine, on the basis of the outside humidity and temperature        values and of the demand for cooling, the operating cost without        the use of water and with a variable use of water, and, on the        basis of the operating cost, to activate a wet operating mode in        which the evaporative cooling means using water 16 are active or        a dry operating mode in which the evaporative cooling means        using water 16 are inactive.

The conditioning unit 11 is, for example, of the indirect free coolingtype, with an air/air exchanger 12.

In a variation of embodiment, the conditioning unit 11 also comprises anauxiliary cooling device 26, which is constituted example by adirect-expansion cooling circuit or constituted by a cooled-watersystem; it is installed within the conditioning unit 11 in order toprovide standby auxiliary cooling power or to supplement the coolingpower supplied by the evaporative cooling means using water 16.

The evaporative cooling means 16 comprise, in the present embodiment:

-   -   nozzles 27 for distributing cooling water within the air/air        exchanger 12,    -   a tank 28 for collecting the water that has not evaporated,    -   one or more recirculation pumps 29 and 30 for drawing water from        the collection tank 28 and sending it toward the nozzles 27.

In a different embodiment, not shown for the sake of simplicity, the airconditioning unit 11 is of the direct free cooling type; in such casethe first fans are arranged in output from an environment to beair-conditioned, and the warm air exits to the outside directly from theenvironment to be air-conditioned.

The conditioning unit 11, in the embodiment described herein, comprisescooling means using water 31 for the secondary air flow 14 at the inletof the conditioning unit 11; such cooling means using water 31 may alsobe absent.

The cooling means using water 31 take the form for example of a seriesof atomization nozzles 32 which are adapted to atomize water in theprimary air flow 13 in the corresponding inlet region 33 of the primaryair flow in the conditioning unit 11.

The atomization nozzles 32 are optionally served by a pressurizationpump 34 which in turn is preceded by a water filter 35.

The atomization nozzles 32 can be substituted by an adiabatic mat, ofconventional type, which performs the same function.

The figures show for the purposes of example a water line 36 for feedingthe conditioning unit 11, which can take the form of a pipe of a watermains or a pipe from another water source.

The temperature and humidity detection means for the primary air flow 13at the inlet of the conditioning unit 11 are constituted by a firstprobe 19, which is arranged so as to intercept the primary air flow 13,which arrives from the environment to be air-conditioned 15, at an inletregion 37 of the conditioning unit 11.

The temperature and humidity detection means for the primary air flow 13at the outlet of the conditioning unit 11, i.e. at an outlet region 38from the unit 11 and at the inlet of the environment to beair-conditioned 15, have a second probe 20.

The means for detecting the temperature and humidity for the secondaryair flow 14 at the inlet of the conditioning unit 11 are constituted bya third probe 21, which is arranged so as to intercept the secondary airflow 14, which arrives from the outside environment, in thecorresponding inlet region 33 of the conditioning unit 11.

The means for detecting the temperature and humidity for the secondaryair flow 14 at the outlet of the conditioning unit 11, i.e. at an outletregion 39 from the unit 11 toward the outside, have a fourth probe 22.

The means for detecting the flow-rate of the primary air flow 13 areconstituted by a fifth probe 23, which is arranged in the outlet region38 from the conditioning unit 11 toward the environment to beair-conditioned 15.

The fifth probe 23 is constituted, for example, by a hot-wireanemometer, or by a differential pressure probe, or by another type ofcommercially-available anemometer adapted to the range of flow-rate andair considered.

The means for detecting the flow-rate of the secondary air flow 14 areconstituted by a sixth probe 24, which is arranged at the outlet region39 of the secondary air flow 14 from the conditioning unit 11 toward theoutside.

Such sixth probe 24 is constituted, for example, by a hot-wireanemometer, or by a differential pressure probe, or by another type ofcommercially-available anemometer adapted to the range of flow-rate andair considered.

The conditioning system 10 according to the invention, once activated,is capable, by way of the electronic control unit 25 and of thedetection means connected thereto, of predictively recalculating whatthe operating cost will be without the use of water or with a variableuse of water; selection of one or the other operating mode is made onthe basis of an instant optimization of the costs.

With the variation of the outside humidity and temperature and of thedemand for cooling, the electronic unit 25 is capable of re-designatingwhat is the most economic operating mode.

This is as applicable to a system according to the invention of thedirect free cooling type as it is to a system according to the inventionof the indirect free cooling type.

The invention also relates to a method of operation for a conditioningsystem 10 according to the invention as described above; the followingsymbols are used hereinbelow:

Tamb=temperature of the outside air used for the free cooling, measuredby the third probe 21;

Hamb=humidity of the outside air used for the free cooling, measured bythe third probe 21;

Tsupply=temperature of the primary air flow 13 at the outlet from theconditioning unit 11 and at the inlet to the environment to beair-conditioned 15, measured by the second probe 20;

Hsupply=humidity of the primary air flow 13 at the outlet from theconditioning unit 11 and at the inlet to the environment to beair-conditioned 15, measured by the second probe 20;

Tret=temperature of the primary air flow 13 at the inlet to theconditioning unit 11, i.e. returning from the environment to beair-conditioned 15, measured by the first probe 19;

Hret=humidity of the primary air flow 13 at the inlet to theconditioning unit 11, i.e. returning from the environment to beair-conditioned 15, measured by the first probe 19;

Tex=temperature of the secondary air flow 14 at the outlet from theconditioning unit 11 toward the outside, measured by the fourth probe22;

Hex=humidity of the secondary air flow 14 at the outlet from theconditioning unit 11 toward the outside, measured by the fourth probe22;

Q1=flow-rate of the primary air flow 13, measured by the fifth probe 23;

Q2=flow-rate of the secondary air flow 14, measured by the sixth probe24.

Such method of operation according to the invention is characterized inthat it comprises the following operations, represented by the blockdiagram in FIG. 3:

-   -   starting the conditioning system 10 (block 40) and detecting, by        way of the detection means, the values of temperature (Tamb,        Tsupply, Tret, Tex), humidity (Hamb, Hsupply, Hret, Hex) and        flow-rate (Q1 and Q2) of the primary air flow and secondary air        flow,    -   determining the cost of dry operation of the system (Cdry),        i.e., without using water, and the cost of wet operation of the        system (Cwet), i.e., using water (block 41);    -   assessing whether the value of the temperature of the outside        environment (Tamb) is lower than a preset temperature value, for        example 18° C., and whether the value of the humidity of the        outside environment (Hamb) is higher than a preset humidity        value, for example 90% (block 42);    -   if either Tamb is lower than the preset temperature value or        Hamb is higher than the preset humidity value, then (block 43)        switching off the evaporative cooling means 16 and the cooling        means using water 31 for the secondary air flow 14 at the inlet,        if they are present;    -   if Tamb is not lower than the preset temperature value and Hamb        is not higher than the preset humidity value, then checking        whether the cost of dry operation of the system (Cdry) is        greater than the cost of wet operation of the system (Cwet)        (block 44);    -   if Cdry is greater than Cwet, then switching on the evaporative        cooling means 16 and/or the cooling means using water 31 (block        45);    -   if Cdry is not higher than Cwet, then checking whether the        temperature of the outside environment (Tamb) is higher than the        return temperature (Tret) of the primary air flow 13 at the        inlet to the conditioning unit 11 (block 46);    -   if the temperature of the outside environment (Tamb) is higher        than the return temperature (Tret) of the primary air flow 13 at        the inlet to the conditioning unit 11, then switching on the        evaporative cooling means 16 and/or the cooling means using        water 31 for the secondary air flow 14 at the inlet (block 45);    -   if the temperature of the outside environment (Tamb) is not        higher than the return temperature (Tret) of the primary air        flow 13 at the inlet to the conditioning unit 11, then switching        off the evaporative cooling means 16 and/or the cooling means        using water 31 for the secondary air flow 14 at the inlet (block        43).

Such cycle of operations is repeated iteratively.

The cost of dry operation of the system (Cdry) is a function of theestimated, or calculated, power (Pdry) absorbed by the fans 17 and 18during the operation of the conditioning unit 11 without using water,i.e. with the evaporative means 16 and the cooling means 31 inactive.

The cost of wet operation of the system (Cwet) is a function of theestimated, or calculated, power (Pwet) absorbed by the fans 17 and 18with the conditioning unit 11 operating using water, and of theconsumption of water W.

In order to determine Pdry, we proceed with the following operations:

-   -   establish a setpoint temperature Ts-p for the cool air        introduced into the environment to be air-conditioned 15 (block        47);    -   detect Tamb, Tret and Q1 (respectively blocks 48, 49 and 50);    -   determine the ratio, in normal dry operation, between the        primary air flow 13 and secondary air flow 14, Rdry, as a        function of Tamb, Tret and Ts-p (block 51):

Rdry=f(Tamb,Tret,Ts-p)

-   -   with the value of Rdry (block 52), determine Q2dry, i.e. the        flow-rate of the secondary air flow 14 for dry operation (block        53), according to a function:

Q2dry=Rdry*Q1

-   -   on the basis of Q2dry, the value indicated by block 54,        determine the estimated speed S2dry for the second fans 18,        according to a function, shown schematically by block 55, of the        type:

S2dry=Cspeed1*Q2dry+Cspeed2

such value shown schematically by block 56, with Cspeed1 and Cspeed2which are coefficients obtained from the characteristics of the fans,

-   -   on the basis of S2dry, determine (block 57) the estimated power        absorbed (Pdry) of the first and second fans 17 and 18 under dry        operation,

Pdry=Cpower1*(S2dry)̂Cpower2

such value shown schematically by block 58, with Cpower1 and Cpower2which are also coefficients obtained from the characteristics of thefans.

In order to determine Pwet, we proceed with the following operations,which are shown schematically in FIG. 5:

-   -   detect Tamb, Hamb, Tret and Q1 (respectively blocks 59, 60, 61        and 62);    -   with Tamb and Hamb, determine the value of the adiabatic        temperature (Tadiab) corresponding to 90% humidity (block 63):

Tadiab=CTA1+CTA2*Tamb+CTA3*(Tamb)̂2+CTA4*(Tamb)̂3

such value shown schematically by block 64, with CTA1, CTA2, CTA3 andCTA4 which are function coefficients of Hamb, obtained from thepsychometric or Carrier chart.

-   -   with Tadiab, Tret, delivery Ts-p (block 66), as established        above, determine Rwet, the ratio, in normal wet operation of the        conditioning unit 11, between the primary air flow 13 and        secondary air flow 14 (block 67):

Rwet=f(Tadiab,Tret,Ts-p)

-   -   with Rwet and Q1 (block 62), determine Q2wet, i.e. the estimated        flow-rate of the secondary air flow 14 for wet operation of the        unit 11 (block 68), according to a function:

Q2wet=Rwet*Q1

-   -   on the basis of Q2wet, the value indicated by block 68,        determine the estimated speed S2wet for the second fans 18,        according to a function, shown schematically by block 69, of the        type:

S2wet=Cspeed1*Q2wet+Cspeed2

-   -   on the basis of S2wet, determine (block 70) the estimated power        absorbed (Pwet) of the first and second fans 17 and 18 under wet        operation of the conditioning unit 11:

Pwet=Cpower1*(S2wet)̂Cpower2

-   -   at the same time as Q2wet, Hamb and Tamb, determine the        flow-rate of water W required for the wet operation of the        conditioning unit 11, i.e. with the evaporative means using        water 16 and the cooling means using water 31, for the secondary        air flow 14, active (block 71):

W=(CW1+CW2*Hamb+CW3*(Hamb̂2)+CW4*(Hamb̂3))*Q2wet+CW5

such value shown schematically with block 72, with the coefficients CW1,CW2, CW3, CW4, CW5 which are obtained from the consumption of water ofthe evaporative cooling means using water 16.

In order to determine Cdry and Cwet, we proceed with the followingoperations, which are shown schematically in FIG. 6:

-   -   determine Cdry by multiplying the calculated value of the power        absorbed in dry operation (Pdry) by a factor Kp which consists        of the cost of electricity (EUR/kW) (blocks 73 and 74):

Cdry=Kp*Pdry

with the operation shown schematically by block 75 and the resultingvalue of Pdry shown schematically by block 76;

-   -   with the values of Kp, Pwet, W, Hamb and a factor Kw which        consists of the cost of water (EUR/(m̂3/hr)) (respectively blocks        74, 77, 78, 79, 80), calculate Cwet (block 81):

Cwet=G*Kw*W+Kp*Pwet

such value shown schematically with block 82, with G which is a factorthat depends on the outside humidity, the value of which is:

G=0.5 for Hamb>45%, high outside humidity and a single pump 29 of theevaporative cooling means using water 16 is in use;

G=0.7 for 30%<Hamb≦45%, average outside humidity and two pumps 29 and 30of the evaporative cooling means using water 16 are in use;

G=1.05 for Hamb≦30%, low outside humidity, two pumps 29 and 30 of theevaporative cooling means using water 16 are in use and, if present,cooling means using water 31 for the secondary air flow 14 at the inletare active.

If Cdry is greater than Cwet, then switch on the evaporative coolingmeans 16 and/or the cooling means using water 31, as in block 45.

If Cdry is not higher than Cwet, but the temperature of the outsideenvironment (Tamb) is higher than the return temperature Tret of theprimary air flow 13 at the inlet to the conditioning unit 11, switch onthe evaporative cooling means 16 and/or the cooling means using water 31for the secondary air flow 14 at the inlet.

If Hamb<90% or Tamb>18° C., the electronic control unit 25 is set toforce the operation of the conditioning unit 11 in dry mode.

When the wet operating mode is selected, if Hamb>45% only one pump 29 ofthe evaporative cooling means 16 is actuated; if Hamb≦45% two pumps 29and 30 of the evaporative cooling means 16 are actuated; if Hamb≦30% twopumps 29 and 30 of the evaporative cooling means 16 are actuated and thecooling means using water 31 for the secondary air flow 14 at the inlet,if present, are active.

The invention also relates to an apparatus for carrying out a method ofoperation of the conditioning system described above.

Such apparatus is characterized in that it comprises:

-   -   means 19, 20, 21, 22, described above, for detecting temperature        and humidity for the primary air flow 13 and the secondary air        flow 14 at the inlet and at the outlet of a conditioning unit        11,    -   means described above 23, 24 for detecting the flow-rate of the        primary air flow 13 and of the secondary air flow 14,    -   an electronic control and management unit 25 adapted to collect        and process the data detected by the detection means 19, 20, 21,        22, 23, 24 and, on the basis of such detected data, adapted to        determine, on the basis of the outside humidity and temperature        values and of the demand for cooling, the operating cost without        the use of water and with a variable use of water, and, on the        basis of the operating cost, to activate a wet operating mode in        which the evaporative cooling means using water 16 are active or        a dry operating mode in which the evaporative cooling means        using water 16 are inactive.

In practice it has been found that the invention fully achieves theintended aim and objects.

Such method of operation of the conditioning system according to theinvention, once operational, on the basis of the readings of thedetection means, is capable of predictively determining what theoperating cost will be without the use of water and what the operatingcost will be with variable use of water.

Selection of one or the other operating mode is made automatically bythe electronic control unit 25 on the basis of an instant optimizationof the costs Cdry and Cwet.

With the variation of the outside humidity and temperature and of thedemand for cooling, the method of operation determines which is the mosteconomic operating mode.

Such method of operation is as valid for systems with direct freecooling as for systems with indirect free cooling, like the onedescribed above.

With the invention a conditioning system and a method for its operationare therefore provided which make possible a continuous optimization ofthe operating costs on the basis of the operating conditions.

In particular, with the invention a conditioning system and a method forits operation are provided which make it possible to vary the parametersconstituted by the local costs of electricity and water if these shouldchange, and to obtain a new optimized solution.

Moreover, with the invention a conditioning system and a method for itsoperation are provided which make it possible to set the automaticselection of the operating mode on the basis of two different costs ofelectricity, a nighttime rate and a daytime rate, so that the electroniccontrol unit can re-parametrize the optimization on the basis of thetime of day.

Furthermore, with the invention a conditioning system and a method forits operation are provided which make it possible to include in the costnot only the power absorbed by the fans and water, but also other,optional backup systems such as a cooling circuit or a refrigeratedwater system, and optimize the cost of the whole.

The invention, thus conceived, is susceptible of numerous modificationsand variations, all of which are within the scope of the appendedclaims. Moreover, all the details may be substituted by other,technically equivalent elements.

In practice the components and the materials employed, provided they arecompatible with the specific use, and the contingent dimensions andshapes, may be any according to requirements and to the state of theart.

The disclosures in Italian Patent Application No. PD2014A000352(102014902318551) from which this application claims priority areincorporated herein by reference.

What is claimed is:
 1. A conditioning system of the free cooling typefor environments and particularly for computing centers, of the typecomprising: a conditioning unit of the free cooling type, which in turncomprises an air/air heat exchanger, inside which two air flows exchangeheat, a primary air flow, from and toward an environment to beair-conditioned, and a secondary air flow, or process flow, drawn fromoutside, and evaporative cooling means using water, first fans formoving said primary air flow, second fans for moving said secondary airflow, wherein said conditioning system comprises: means for detectingtemperature and humidity for the primary air flow and the secondary airflow at the inlet and at the outlet of said conditioning unit, means fordetecting the flow-rate of the primary air flow and of the secondary airflow, an electronic control and management unit adapted to collect andprocess the data detected by said detection means and, on the basis ofsuch detected data, adapted to determine, on the basis of the outsidehumidity and temperature values and of the demand for cooling, theoperating cost without the use of water and with a variable use ofwater, and, on the basis of the operating cost, to activate a wetoperating mode in which the evaporative cooling means using water areactive or a dry operating mode in which the evaporative cooling meansusing water are inactive.
 2. The conditioning system according to claim1, wherein said evaporative cooling means comprise: nozzles fordistributing cooling water within said air/air exchanger, a tank forcollecting the water that has not evaporated, one or more recirculationpumps for drawing water from said collection tank and sending it towardsaid nozzles.
 3. The conditioning system according to claim 1, whereinsaid conditioning unit comprises cooling means using water for thesecondary air flow at the inlet of the conditioning unit.
 4. Theconditioning system according to claim 1, wherein said means fordetecting the temperature and humidity for the primary air flow at theinlet of the conditioning unit are constituted by a first probe, whichis arranged so as to intercept the primary air flow, which arrives fromthe environment to be air-conditioned, at an inlet region of saidconditioning unit.
 5. The conditioning system according to claim 4,wherein said means for detecting the temperature and humidity for theprimary air flow at the outlet of the conditioning unit have a secondprobe.
 6. The conditioning system according to claim 5, wherein saidmeans for detecting the temperature and humidity for the secondary airflow at the inlet of the conditioning unit are constituted by a thirdprobe, which is arranged so as to intercept the secondary air flow,which arrives from the outside environment, at a corresponding inletregion of the conditioning unit.
 7. The conditioning system according toclaim 6, wherein said means for detecting the temperature and humidityfor the secondary air flow at the outlet of the conditioning unit, at anoutlet region from the unit toward the outside, have a fourth probe. 8.The conditioning system according to claim 7, wherein said means fordetecting the flow-rate of the primary flow are constituted by a fifthprobe, which is arranged at the outlet region from the conditioning unittoward the environment to be air-conditioned.
 9. The conditioning systemaccording to claim 8, wherein said means for detecting the flow-rate ofthe secondary air flow are constituted by a sixth probe, which isarranged at the outlet region of the secondary air flow from theconditioning unit toward the outside.
 10. A method of operation of aconditioning system according to claim 1, comprising the followingoperations: starting the conditioning system and detecting, by way ofthe detection means, the values of temperature, humidity and flow-rateof the primary air flow and secondary air flow, determining the cost ofdry operation of the system, i.e., without using water, and the cost ofwet operation of the system, i.e., using water; assessing whether thevalue of the temperature of the outside environment is lower than apreset temperature value and whether the value of the humidity of theoutside environment is higher than a preset humidity value; if eitherthe temperature of the outside environment is lower than the presettemperature value or the humidity of the outside environment is higherthan the preset humidity value, then switching off the evaporativecooling means and the cooling means using water for the secondary airflow at the inlet, if they are present, if the temperature of theoutside environment is not lower than the preset temperature value andthe humidity of the outside environment is not higher than the presethumidity value, then checking whether the cost of dry operation of thesystem is greater than the cost of wet operation of the system; if thecost of dry operation of the system is higher than the cost of wetoperation of the system, then switching on the evaporative cooling meansand/or the cooling means using water, if present; if the cost of dryoperation of the system is not higher than the cost of wet operation ofthe system, then checking whether the temperature of the outsideenvironment is higher than the return temperature of the primary airflow at the inlet to the conditioning unit; if the temperature of theoutside environment is higher than the return temperature of the primaryair flow at the inlet to the conditioning unit, then switching on theevaporative cooling means and/or the cooling means using water for thesecondary air flow at the inlet, if they are present; if the temperatureof the outside environment is not higher than the return temperature ofthe primary air flow at the inlet to the conditioning unit, thenswitching off the evaporative cooling means and/or the cooling meansusing water for the secondary air flow at the inlet, if they arepresent.
 11. The method of operation according to claim 10, wherein:said cost of dry operation of the system is a function of the estimatedpower absorbed by the fans during the operation of the conditioning unitwithout using water; said cost of wet operation of the system is afunction of the estimated power absorbed by the fans with theconditioning unit operating using water, and of the consumption ofwater.
 12. An apparatus for carrying out a method of operation of aconditioning system according to claim 1, comprising: means fordetecting temperature and humidity for the primary air flow and thesecondary air flow at the inlet and at the outlet of a said conditioningunit, means for detecting the flow-rate of the primary air flow and ofthe secondary air flow, an electronic control and management unitadapted to collect and process the data detected by said detection meansand, on the basis of such detected data, adapted to determine, on thebasis of the outside humidity and temperature values and of the demandfor cooling, the operating cost without the use of water and with avariable use of water, and, on the basis of the operating cost, toactivate a wet operating mode in which the evaporative cooling meansusing water are active or a dry operating mode in which the evaporativecooling means using water are inactive.